Population 638 Demography 122 Congresses 110 Population Economics 109 Fish populations 106 Population genetics 102 Ecology 95 more ... Animal populations 85 Population biology 85 Birth control 74 Mathematical models 72 Statistics 69 Population policy 68 Biomathematics 58 Genetics and Population Dynamics 51 Addresses, essays, lectures 50 Economic aspects 46 Community & Population Ecology 45 Community ecology, Biotic 44 Periodicals 39 Food supply 35 Population research 33 Agriculture 32 Plant populations 31 Statistical methods 30 Economic conditions 27 Sociology 27 Statistics  27 Bird populations 26 Emigration and immigration 26 less ...